Loop-taker mechanism for sewing machines



July 27, 1948. A. R. WOOD 4 2,446,150

LOOP-TAKER MECHANISM FOR SEWING MACHINES Original Filed Aug. 21, 1945 93% 1E WWA axiom 1 Patented July 27, 1948 LOOP-TAKER MECHANISM FOR SEWING MACHINES Alfred R. Wood, Bridgeport, Conn, assignor to The Singer Manufacturing Company, Elizabeth, N.J., a corporation of New Jersey Original application August 21, 1945, Serial No. 611,724. Divided and this application June 22, 1946, Serial No. 678,618 p This invention relates to improvements in sewing machines, and more particularly to mechanical opener devices employed in connection with sewing machine loop-takers for providing an unobstructed passage around a thread-mass carrier for needle-thread loops cast thereabout by the loop-taker; the invention having for its primary object better to adapt devices of this character to operate at high speed with a minimum of noise.

' The foregoing and other objects and advantages in view, together with means whereby the same maybe carried into effect, will best be understood from the following description of a preferred embodiment thereof illustrated in the accompanying drawings, inwhich Fig. 1 represents a front elevational view, partly in section, of a sewing machine equipped with my improved mechanical opener device.

Fig. 2 represents a vertical sectional view taken substantially along the line 2-2, Fig. 1, illustrating the operating mechanism for the mechanical opener.

Fig. 3 represents a vertical sectional view taken substantially along the line 3- 3, Fig. 2. p

Fig. 4 represents a right side elevational view, partly in section, of the stitch-forming instrumentalities, showing the bobbin-thread pull-off blade in its maximum thread pull-off position.

This application is a division of myco-pending application SerialNo. 611,724, filed August 21,

1945, now Patent No. 2,438,833, March 30, 1948.

Referring more in detail tothe drawings, the invention is shown as embodied in a buttonhole sewing machine constructed substantially in accordance with that forming the subject of my U. 5. Patent No. 2,411,493, dated November 19, 1946. The machine has a frame including a bed I I provided with a depending supporting lug l2. Journaled in a bushing l3 pressed into the supporting.

lug I2 is a rotary loop-taker shaft I4 geared to be operated by an arm shaft (not shown) at a speed twice that of the arm-shaft. ,As clearly sh'own in my above mentioned patent, the arm-shaft is connected at the head-end of the machine to endwise reciprocate a thread-carrying needle 15 which is adapted to be vibrated in a direction crosswise of the bed l|. Cooperating with the needle 15 in the formation of lockestitches is a loop-taker, indicated generally as 16, of the rotary hook lockstitch typ which loop-taker is fast on the rotary shaft [4.

The work to be buttonholed is adapted to be held in a work-clamp. comprising the usual'lower workplate I1 and the upper clamp-foot I 8, 1. The work-clamp is adapted to be movedin 7 Claims. (Cl. 112-228) step-by-step fashion under the endwise reciprocatory and laterally vibratory needle l5, and relativetothe usual needle-aperture IS in the throat-plate 20, first away from the machinestandard and then towards the machine-standard to cause the first and second rows of side zig- .za stitches to be laid side by side in the work.

The mechanism for imparting to the work-clamp its traveling movements is fully disclosed in my previously mentioned U. S. Patent No. 2,411,493, and therefore no further description will be made herein of said mechanism. if

As previously indicated, the stitch-forming mechanism of the machine illustrated comprises the endwise reciprocatory and laterally vibratory thread-carrying needle l5 and the complemental rotary hook l6. The rotary hook is adapted to seize the thread-loop presented by the needle and expand such loop for passing it about the under thread-mass contained in the stationary threadmass enclosing means of the rotary hook. The thread-mass enclosing means shown in the drawings forms the subject of my U. S. Patent No. 2,419,698, dated April 29, 1947, and therefore only sufficient reference will be made in this case to this means as will berequired to give anunderstanding of the operation of the present invention. Sufiice it to say that the thread-mass enclosing means comprises a cup-shaped carriermember 2| and a telescopically disposed threadcase 22, defining between them a thread-mass cavity into which is inserted the usual bobbin or cop. To restrain the thread-mass enclosing means against rotation with the rotary loop-seizing beak of the loop-taker, the carrier-member 2 has extending upwardly from its periphery a s'ubstantially C-shaped projection 23, the upper por tion of which is adapted to extend between the free ends of a pair of stop-plates 24 and 215 (Fig.

l), adjustably secured to the bed H 01- the ma chine-frame. The C-shaped projection 23 is vertically channeled to receive a correspondingly shaped upstanding projection 26 formed on the thread-case 22.

Disposed to operate between the spaced bobbinthread-directin guides defined by the upper and lower limbs 21 and 28 of the C-shaped projection 26 (Fig. 4 is a curved thread pull-off blade 29 formed adjacent its free end with a thread-cam edge 30. At its other end, the pull-ofi blade 29 merges into an offset shank 3| (Fig. 2) provided with an elongated hole 32 and an inturned posi-.

tioning lip33; the lip being adapted to enter a slot 34 formed in the outer end of a carrier-lever 35 which embraces and is freely journaled at'its inner end on the exposed end of the hook-shaft bushing l3. A clamp screw 36 passing through the elongated hole 32 and threaded into the carrier-lever 35 adjustably secures the blade 29 to said lever 35. The lip 33, when disposed in. the. slot 34, prevents the pul1-off blade 29 from turn-- ing about the clamping screw 36. As the carrierlever 35 is actuated to fulcrum on the periphery of the hook-shaft bushing I 3, the pull-off blade 29 moves into and out of thread-engaging position between the limbs 21 and 28 of the C-shaped projection 23. When the pull-oh blade. 29 is advanced from its retracted position, showninfull-- lines in Fig. 3, to its advanced positiomshown in. dotted lines in the same figure, the thread-cam edge 3|] is adapted to contact and deflect laterallythe portion of the bobbin-thread leading from the lower to the upper limb of the C-shaped projection 26 and form a bight in the thread between the limbs of the projection, in the manner shown in- Fig. 4. The blade 29-,. in forming the bight in the bobbin-thread, draws from the supply within thethread-case 22 a length of thread sufficient to form abobbin-thread loop of a size such that it may be pulled through to-the upper side of the work so that in the finished scam the needlethread will lie in substantially a straight line adjacent the buttonhole slit. It will be noted that the limbs 21' and 28 of the C-shaped projection 23 are rather closely spaced apart. This is advantag-eous for the reason that the bobbin-thread extending between the limbs 27- and 28 is relatively short. It is, in fact, so short that, when the thread-cam edge 3|] of the pull-01f blade engages the thread, any inherent elasticity in the thread does not militate against the drawing of a uniform length of thread from the supply during each stroke of the pull-off blade.-

The mechanism for actuating the bobbinthread' pull-01f blade 29 preferably comprises a counter-balanced crank. 31 (Fig. 3-) having a crank-pin 38 connected by a link 39 to a pin 49' threaded into the carrier-lever 35. The counterbalanced crank31 is carried on the outer end of a horizontally disposed rotary actuating shaft: 4|

journaled in a bearing bushing 42 pressed into the supportinglug l2. Secured on the other end of the actuating shaft 4| is a gear 43 in mesh with ahalf-size gear 44 fast on the hook-shaft 14. Through the mechanism just described, rotation of the hook-shaft I4 imparts to the actuating shaft 4|, through the gearing 43 and 44, rotary movements at one half the speed of the hookshaft. In other words, the pull-off blade 29 is given one complete to-and-fro actuation for each stitch-forming cycle. As the actuating shaft. is rotated, the counterbalanced. crank 31 imparts to the carrier-lever 35, through the link 39 and pin 40, a motion causing the carrier-lever to oscillate about the bushing I3. The pull-oil? blade 29, which is secured to the carrier-lever, is thereby swung about the axis of the rotary hook I6 and is timed to begin its advance as the needle is starting down and to complete its advance at about the time the needle reaches the limit of its downstroke. ,The pull-ofi blade 29 dwells in its advanced position (dotted lines in Fig. 3) while the needle isthrowing out a loop of upper thread for seizure by the rotary hook 6. The pulloff then retracts so that slack bobbin-thread is available to be absorbed into the next stitch when the needle-loop is pulled up by the usual needlethread take-up mechanism. At the time of initial engagement of the pull-ofi blade 29 with the bobbin-thread, said blade is moving at a speed considerably less than that of the rotary hook Hi. This fact, coupled with the gradual incline of the thread-cam edge 30, results in the pull-off blade engaging the bobbin-thread with a smooth action, thus. avoiding a. jerking oi thebobbin-thread and minimizing any tendency toward over-running or spilling of thread by the bobbin or cop.

Provision is made for rendering the pull-off blade 29 ineifective during the sewing of the barring stitches: at each end of the buttonhole so that the locking points of these stitches Will not be. pulled through the work as are the side stitches of thebuttonhole. To this end, the Working position or thecarrierdever 35 is shifted longitudinally of the bushing l3 so that the free end of the pull-off blade will, in its advance, miss the bobbinethread, as: shown in my co-pending application Serial No. 611,724, of which this is a division- To effect this shifting of the pull-off blade 29, the hub of the carrier-lever 35 is formed with a circumferential groove 45 which is..cntered--by thev half-round recessed portion of an arm 5 (Fig. 3.) ona slide-shaft. 47 journaled in the supe porting lug 12.. At. its. rearward end, the slide.- shaft 41 has adjustably fastened on it ahead 48. adapted to be contacted by a-roller 49 j curnaled on the free end of a horizontally disposed swing lever 5|]; pivoted on a stud 5| threaded into. the. bed The lever 50, at itsv free end,.adjustably carries a cam-follower 52 disposed to beeneaeed by a cam-section 53 secured on the usual feedcam (not shown)... In the. operation, of the. ma-% chine, the. feed-cam is rotated once during, each complete butt-onholing cycle. When the cam-secr tion 53 on the feed-cam engages the cam-fob lower 52,. the swing-lever 50 is movedin a direction away from the feed-cam, causing the roller 49 to move into engagement with thehead 48. of the slide-shaft 41 and shift the same outwardly against the action of a coil-spring 5.4 acting be.- tween a collar 55 on the slide-shaftandthe supporting lug l2. When the slide-shaft 4'| isshifted, the carrier-lever 55, through the medium .of the arm 46,, is moved outwardly on the bearing bushing |3 and to the extent that the point of the pull-01f blade 3'| entirely misses the bobbinthread and no bobbin -thread is pulled ofi during the formation of the barring stitches. After the completion of the last. barring. stitch and the cam section 53 has moved beyond the cam-follower 52, the coil-spring 54 actsv to return the pull-ofi blade 29' to its effective position, which position is determined by the hub of thearm 46 striking the supporting lug l2. It will be understood that the pin 4!) slides relative to the upper end of the link 39 during the shifting of the pull-off blade and, consequently, the driving relationship of the pull-01f blade actuatingmechanism is not interrupted. It will be understood thatthe timi fl the shift of the pull-off blade from effective to ineffective position can be regulated by virtue of the adjustment of the cam-follower 52 on the swing-lever 50. Moreover, the ineffective position of the pull-off blade can be accurately determined by adjusting the head 48 lengthwise of the slide-shaft 41.

As mentioned above, the bobbin supply is adapted to be housed in a thread-mass enclosing means including a thread-case22 and a carrier 2| therefor; the thread-case and carrier being restrained against rotation with the rotary loop-taker. I6 by means of the loosely interengaging projection 23 and stop-plates 24 and 25. As a resultof the frictional drag between the'bearing rib on the thread.- case carrier and the raceway in the loop-taker,

5 the thread case and its carrier have a normal tendency to rotate with the loop-taker, thereby causing the rotation-restraining projection 23 to bearagainst the stop-plate 25, In order to "obtain a free passage on each; side of theprojection 23 for the unobstructed free travel of the needle thread loopabout the thread-case and its carriehduring stitch-formation, the thread-case and its carrier are intermittently, oscillated, to a limited extent, ina direction opposite to the di-- rection of rotation of the loop-taker. This osci1- lation is effected by means of a mechanical opener comprising an opener-arm, 56 (Figs. 1 and 2) which is adjustably clamped at its lowerend in a split socket-member 51 fast on the outer end of a rock-shaft 58 journalled in a horizontal bushing 59 pressed into the supporting lug 12. At its upper end, the opener-arm 56 is bent or oilset, as at 60, to provide a hook-shaped end extending toward the thread-case 2|; the hook-- shaped end being notched, as at 6!, Fig. 1, to form spaced resilient fingers 62 and 63 adapted to enter an opener-finger receiving pocket 64 formed in the thread-case carrier 2| on the cast-on side thereof. The fingers 52 and 63, as shown in Fig.

62 with one side of the thread-case carrier pocket B4 to initiate an oscillation of the thread-case carrier in a direction reverse to the direction of rotation of the hook-body, and that following this engagement the lower finger 63 resiliently engages the other side of the pocket 64, whereby the rotation-restraining projection 23 is maintained stationary substantially midway between the stop-plates 24 and 25. The spaced resilient fingers 62 and B3 serve to provide a relatively noiseless mechanical opener, as well as one which maintains the rotation-restraining projection on the thread-mass enclosing means stationary and in position such that an open thread passage exists on both sides of the projection for the free unobstructed travel of the needle-thread loop.

The opener-arm rock-shaft 58 is actuated by means of a rock-lever 65 which is connected to one end of a short pitman 56 embracing at its other end an eccentric 6'! preferably integral with the gear 43. Separating the pitman 66 from the end of the bushing 42 is a disk 58 secured to the eccentric 61 by a screw 69, (Fig.

From the above description taken in connection with the accompanying drawings, it will be understood that I have devised a mechanical opener mechanism in which the thread-case carrier engaging means includes spaced resilient fingers adapted to engage spaced shoulders on the thread-case carrier with a smooth cam-like action, reducing to a, minimum the noise of impact between th fingers and the thread-case carrier. Also, after the fingers have moved into engagement with the shoulders on the thread-case carrier, the rotation-restraining projection on the thread-case carrier is firmly held spaced from the oppositely disposed stop-plates 24 and 25, whereby a free thread-passageway is provided for the needle-thread loop.

Having thus set forth the nature of the invention, what I claim herein:

1. In a lock-stitch sewing machine, a reciprocatory thread-carrying needle, a rotary loop-taker, a thread-mass carrier journaled in said rotary loop-taker and having a pocket formed therein, means for restraining rotation of said threadpair of resilient fingers adapted spaced shoulders, meansfor restraining rotation of said thread-mass carrier with said 'loopetaker,

andm'eans for opening a thread passage past said rotation-restraining means including an openerme'mber having a pair of fingers, one of said fin gers being adapted to engage one of said shoulders to initiate oscillation of the thread-mass carrier in a direction reverse to the direction of rotation of said loop-taker and the other of said fingers adapted to engage the second shoulder to arrest the oscillation of said thread-mass carrier.

3. In a lock-stitch sewing machine, a reciprocatory thread-carrying needle, a rotary loop-taker cooperating with said needle in the formation of stitches, a thread-mass carrier juornaled in said loop-taker, means for restraining rotation of said thread-mass carrier with said loop-taker, and means for opening a thread passage past said rotation-restraining means including an opener-member engageable with said threadmass carrier to initiate oscillation of the threadmass carrier in a direction reverse to the direction of rotation of said looptaker and again to.

engage said thread-mass carrier to arrest the oscillation of said thread-mass carrier so that an open thread passage exists on opposite sides of the rotation-restraining means.

4. In a lock-stitch sewing machine, a reciprocatory thread-carrying needle, a rotary looptaker cooperating with said needle in the formation of stitches, a shaft carrying said toop-taker, a thread-mass carrier journaled in said looptaker, means for restraining rotation of said thread-mass carrier with said loop-taker, and means for opening a thread passage past said rotation-restraining means including an openerarm, a rock-shaft supporting said opener-arm and arranged substantially parallel with said loop-taker shaft, a rock-lever fast on said rockshaft, an eccentric geared to said loop-taker shaft to rotate at one half speed of the loop-taker shaft, and a pitman connecting said eccentric with said rock-lever.

5. In a lock-stitch sewing machine, a reciprocatory thread-carrying needle, a rotary looptaker, a thread-mass carrier journaled in said loop-taker and having opposed shoulders formed thereon, means for restraining rotation of said thread-mass carrier with said loop-taker, and a mechanical opener for providing a thread passage past said rotation-restraining means, said mechanical opener including an opener-arm having an offset free end longitudinally notched to provide a pair of resilient fingers adapted to engage the opposed shoulders on said threadmass carrier.

6. In a lock-stitch sewing machine, a reciprocatory thread-carrying needle, a rotary loop-taker cooperating with said needle in the formation of stitches, a shaft carrying said loop-taker, a thread-mass carrier journaled in said loop-taker and having opposed shoulders formed thereon,

means for restraining rotation of said thread- 

